Heat source systems that are provided with a plurality of heat source apparatuses, such as centrifugal chillers etc., are conventionally known for achieving district cooling/heating, cooling/heating in factories etc., and so forth. These heat source systems control the number of operating heat source apparatuses in accordance with the heat demand required by external loads. Upon performing this number-of-units control, It is required to achieve an energy saving by operating the heat source apparatuses at high efficiency.
PTL 1 discloses a technology in which an inverter is controlled in such a manner that the coefficient of performance is equal to or more than a predetermined value by obtaining the relationship between the load factor and the coefficient of performance of an inverter-driven centrifugal chiller, which is determined by the cooling water temperature supplied to a condenser.